Defensive coordinator John Pagano, as expected, is returning to the Chargers, as are three other coaches from the team’s defensive staff.

In reality, Pagano never left, but with the team’s turnover at head coach, it wasn’t until Friday that the club announced he’ll be on Mike McCoy’s staff. Pagano, meantime, said he’d stayed in San Diego since the Chargers’ final game.

“Can’t wait to get back to work,” he said. “All I want to do is coach football. That’s what I’m about.”

It’s also expected that McCoy will hire former NFL passer Frank Reich as his quarterbacks coach. Reich last year was the Cardinals’ receivers coach under head man Ken Whisenhunt, the Chargers’ new offensive coordinator.

Norv Turner last year promoted Pagano, who’d been the team’s linebackers coach since 2005, into the coordinator job.

After Turner was fired three weeks ago, Chargers higher-ups continued to praise Pagano, who was under contract for 2013.

McCoy, hired as head coach on Tuesday, didn’t let a week pass before securing the coordinator, whose defense scored seven touchdowns, second in the NFL to the Bears’ 12, and finished 16th in points allowed. A Chargers strength was the run defense, which finished fifth in yards per carry and sixth in yards. Against the pass, the Chargers ranked 18th in yards allowed.

Pagano, 45, said he’s eager to build on last season.

“It’s about getting the guys to (work) every day: fundamentals, technique and effort,” he said. “It’s about being accountable, communication and trust. That’s going to keep us growing as a defense.”

Both Reich and his new lead pupil, Philip Rivers, are looking to rebound from disappointing seasons.

Then again, epic comebacks are a specialty of Reich’s, who as Maryland’s quarterback led Bobby Ross’ Terrapins from a 31-0 halftime deficit past Miami in 1984. Eight years later, Reich rallied the Bills past the Oilers, who’d led the 1992 NFL playoff game 35-3 in the third quarter.

Reich, 51, was a receivers coach the last two years, allowing him to work with two of the NFL’s elite wideouts in Reggie Wayne (Colts) and Larry Fitzgerald (Cardinals).

But disarray at quarterback and in the offensive line plagued both teams, whose offenses ranked among the NFL’s worst performers. After each season, the coaching staff was fired, Reich included.

Whisenhunt brought Reich to the Cardinals, who last year fell apart after starting out 4-0. Arizona quarterbacks took 58 sacks, the most in the NFL, and the offense ranked 31st in scoring and last in yards per play.

Reich, whose receivers included Michael Floyd, who was drafted thirteenth last April, defended Whisenant after the team’s 5-11 season.

“There are not a lot of coaches that have been real successful in Arizona,” he told WGR Sports Radio 550 in Buffalo in early January. “‘Whis’ took a team to the Super Bowl there — that says a lot. Obviously, I think I have a good relationship with ‘Whis,’ and I would be knocking on his door if he got the job.”

As has McCoy, who was Denver’s offensive coordinator from 2009-12, Reich has coached Peyton Manning, doing so as the Colts’ quarterbacks coach in 2009-10. Manning joined the Broncos last year, and the Chargers went 0-2 against Denver for the first time since 2005.

In Rivers’ seven seasons as a starter, the Chargers’ quarterbacks coach was John Ramsdell, who’d worked with Kurt Warner in St. Louis.